There is plenty of dirt at the plant in Barking, Essex, the biggest in Europe. About 220 million gallons of human waste flows into Beckton every day from 3 million Londoners who live north of the river Thames.
The methane gas produced naturally during the treatment process generates electricity to run the works. But soon, it will also contribute to the National Grid.
Yesterday a power house, modernised and automated at a cost of pounds 10m over the past 12 months, was opened. It will enable Thames to eventually produce eight megawatts of electricity, enough to supply 6,000 households. Early next year the plant will export electricity to the National Grid through a contract awarded under the Government's 'green energy' programme.
Tony De-Seta, Thames project manager, said Beckton was the largest power plant on a sewage treatment works outside the United States. 'And doesn't it smell lovely?'
During the treatment process, naturally occurring bacteria munch on the sewage and clean the water, which is then discharged into the Thames - about a tonne of it every day, making Beckton the river's biggest tributary.